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Restless Genes - National Geographic Magazine

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The compulsion to see what lies beyond that far ridge or that ocean—or this planet—is a defining part of human identity and success.


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We explore because of our genes?

"No other mammal moves around like we do,” says Svante Pääbo, a director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, where he uses genetics to study human origins. “We jump borders. We push into new territory even when we have resources where we are. Other animals don’t do this. Other humans either. Neanderthals were around hundreds of thousands of years, but they never spread around the world. In just 50,000 years we covered everything. There’s a kind of madness to it. Sailing out into the ocean, you have no idea what’s on the other side. And now we go to Mars. We never stop. Why?”

Why indeed? Pääbo and other scientists pondering this question are themselves explorers, walking new ground. They know that they might have to backtrack and regroup at any time. They know that any notion about why we explore might soon face revision as their young disciplines—anthropology, genetics, developmental neuropsychology—turn up new fundamentals. Yet for those trying to figure out what makes humans tick, our urge to explore is irresistible terrain. What gives rise to this “madness” to explore? What drove us out from Africa and on to the moon and beyond?

If an urge to explore rises in us innately, perhaps its foundation lies within our genome. In fact there is a mutation that pops up frequently in such discussions: a variant of a gene called DRD4, which helps control dopamine, a chemical brain messenger important in learning and reward. Researchers have repeatedly tied the variant, known as DRD4-7R and carried by roughly 20 percent of all humans, to curiosity and restlessness. Dozens of human studies have found that7R makes people more likely to take risks; explore new places, ideas, foods, relationships, drugs, or sexual opportunities; and generally embrace movement, change, and adventure. Studies in animals simulating 7R’s actions suggest it increases their taste for both movement and novelty. (Not incidentally, it is also closely associated with ADHD.)

Most provocatively, several studies tie 7Rto human migration. The first large genetic study to do so, led by Chuansheng Chen of the University of California, Irvine in 1999, found 7R more common in present-day migratory cultures than in settled ones. A larger, more statistically rigorous 2011 study supported this, finding that 7R, along with another variant named 2R, tends to be found more frequently than you would expect by chance in populations whose ancestors migrated longer distances after they moved out of Africa. Neither study necessarily means that the 7R form of the gene actually made those ancestors especially restless; you’d have to have been around back then to test that premise with certainty. But both studies support the idea that a nomadic lifestyle selects for the 7R variant.

Another recent study backs this up. Among Ariaal tribesmen in Africa, those who carry 7R tend to be stronger and better fed than their non-7R peers if they live in nomadic tribes, possibly reflecting better fitness for a nomadic life and perhaps higher status as well. However,7R carriers tend to be less well nourished if they live as settled villagers. The variant’s value, then, like that of many genes and traits, may depend on the surroundings. A restless person may thrive in a changeable environment but wither in a stable one; likewise with any genes that help produce the restlessness.

So is 7R the explorer’s gene or adventure gene, as some call it? Yale University evolutionary and population geneticist Kenneth Kidd thinks that overstates its role. Kidd speaks with special authority here, as he was part of the team that discovered the 7R variant 20 years ago. Like other skeptics, he thinks that many of the studies linking 7R to exploratory traits suffer from mushy methods or math. He notes too that the pile of studies supporting 7R’s link with these traits is countered by another stack contradicting it.

In just 50,000 years we covered everything. That's amazing. 

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